(a) Field of the Invention
The present invention relates to a method and device for transmitting media data in a digital broadcasting system.
(b) Description of the Related Art
Regarding next-generation broadcasting standards such as the digital video broadcasting (DVB)-T2, and the advanced television systems committee (ATSC) 3.0 that is currently undergoing the progress of standardization, a single broadcasting channel may be configured with a plurality of subchannels (e.g., physical layer pipes (PLP) in the DVB-T2 system) for independently performing modulation and channel coding, differing from the existing digital broadcasting standards based on the moving picture experts group (MPEG)-2 system. The difference may influence a method for loading a media stream on a broadcasting channel having a limited transmission bit ratio and complexity thereof.
The conventional digital broadcasting standard allows transmitting media through a multiplexed MPEG-2 transmission stream matching a limited transmission bit ratio of a broadcasting channel. Therefore, to compensate for a change of the transmission bit ratio of the input media, a null packet is inserted and the transmission bit ratio of the MPEG-2 transmission stream is fixed.
However, the next-generation broadcasting standard may not use the null packet in the MPEG-2 transmission stream so as to maximize transmission efficiency, and may support transmission of media data of an internet protocol (IP) in which it is difficult to guarantee a fixed transmission bit ratio. Hence, the respective subchannels of the next-generation broadcasting standard does not have a fixed transmission bit ratio so it is difficult to load the media stream on the broadcasting channel according to the conventional method. That is, when the broadcasting channel includes a plurality of subchannels with different transmission bit ratios, the subchannels need to be efficiently allocated to a restricted broadcasting resource (i.e., a transmission frame). Particularly, the broadcasting resource needs to be more efficiently allocated for the stream (e.g., video stream) in which it is difficult to anticipate a temporal change of the transmission bit ratio.
In addition, a data size of each frame is different in the case of a video stream configured with data having a constant time gap, so when the video stream is transmitted with reference to an average data rate of the stream, a transmission delay time of each frame is changed (that is, a delay jitter is generated). A receiving end of the broadcasting system must control a buffer and synchronize the time so as to compensate the change of a frame transmission delay time, and the buffer controlling and the time synchronization may become more complicated when there are a plurality of subchannels.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.